Many prior art reports of ammoniacal leaching have used tank or vat leaching, in which the ore or concentrate is simply immersed directly into ammoniacal solution.
Although many methods for ammoniacal leaching are described in the literature, including the patent literature, all require one or more of multiple leaching stages, energy-intensive pre-treatment of the ore (for example roasting or grinding) and/or elevated leach temperatures and/or pressures. These requirements necessitate complicated engineering and significant energy consumption, so it is little surprise that none have been widely adopted.
Further, many ammoniacal leaching methods either suffer from significant ammonia loss, or require complicated chemistry or engineering to overcome such, providing a further impediment to the widespread adoption of ammoniacal leaching methods.
The method of leaching of the present invention has as one object thereof to overcome the abovementioned problems associated with the prior art, or to at least provide a useful alternative thereto.
Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.
The discussion of the background art is included exclusively for the purpose of providing a context for the present invention. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was common general knowledge in the field relevant to the present invention in Australia or elsewhere before the priority date.